It is important to detect a load that each machine piece that configures a machine receives, in grasping the state of the machine and in performing drive control of the machine. Conventionally, as a load detecting device that detects a load that acts on a coupling pin of mechanism members combined into a link, one that uses a pin-type load cell in which a load detection function is provided to the coupling pin itself of the mechanism members has been known. The pin-type load cell is inserted into a coupling unit of mechanism members, and detects a load that acts on the coupling unit.
It is essential, in a working machine such as a hydraulic excavator, to measure a load that acts on an attachment part in order to grasp a work amount and ensure safety. Patent Literature 1 proposes, as a pin-type load cell that is suitable for this type of a working machine, one that is provided with a pin hole provided in the axial direction of a pin, and with two strain sensors that are positioned on the same circumference in the wall surface of this pin hole or the outer periphery of the pin, and are mounted on two mutually orthogonal surfaces, one strain sensor for each surface, and has a value of the diameter of the pin hole/the outer diameter of the pin of 0.2 or smaller. Because the pin-type load cell described in Patent Literature 1 prevents deformation of the cross-sectional shape of the pin due to a load by controlling the diameter of the pin hole, it is possible to measure a load that acts on the pin highly accurately even when the direction of action of the load changes.